Simulation of the extreme waves generated by typhoon Bolaven (1215) in the East China Sea and Yellow Sea

Record-breaking high waves occurred during the passage of the typhoon Bolaven (1215) (TYB) in the East China Sea (ECS) and Yellow Sea (YS) although its intensity did not reach the level of a super typhoon. Winds and directional wave measurements were made using a range of in-situ instruments mounted on an ocean tower and buoys. In order to understand how such high waves with long duration occurred, analyses have been made through measurement and numerical simulations. TYB winds were generated using the TC96 typhoon wind model with the best track data calibrated with the measurements. And then the wind fields were blended with the reanalyzed synoptic-scale wind fields for a wave model. Wave fields were simulated using WAM4.5 with adjustment of C_d for gust of winds and bottom friction for the study area. Thus the accuracy of simulations is considerably enhanced, and the computed results are also in better agreement with measured data than before. It is found that the extremely high waves evolved as a result of the superposition of distant large swells and high wind seas generated by strong winds from the front/right quadrant of the typhoon track. As the typhoon moved at a speed a little slower than the dominant wave group velocity in a consistent direction for two days, the wave growth was significantly enhanced by strong wind input in an extended fetch and non-linear interaction.     

Development of a skill assessment tool for the Korea operational oceanographic system

A standard skill assessment(SA) tool was developed and implemented to evaluate the performance of operational forecast models in the Korea operational oceanographic system.The SA tool provided a robust way to assess model skill in the system by comparing predictions and observations,and involved the computation of multiple skill metrics including correlation and error skills.User-and system-based acceptance criteria of skill metrics were applied to determine whether predictions were acceptable for the system.To achieve this,the tool produced a time series comparison plot,a skill score table,and an advanced summarized diagram to effectively demonstrate the multiple skill scores.Moreover,the SA was conducted to evaluate both atmospheric and hydrodynamic forecast variables.For the atmospheric variables,acceptable error criteria were preferable to acceptable correlation criteria over short timescales,since the mean square error overwhelmed the observation variance.Conversely,for the hydrodynamic variables,acceptable root mean square percentage error(e.g.,p erms) criteria were preferable to acceptable error(e.g.,erms) criteria owing to the spatially variable tidal intensity around the Korean Peninsula.Furthermore,the SA indicated that predetermined acceptance error criteria were appropriate to satisfy a target central frequency(fc) for which errors fell within the specified limits(i.e.,the fc equals 70%).     

Distribution and Acoustic Characteristics of Shallow Gas in the Korea Strait Shelf Mud off SE Korea

Shallow gas in the Korea Strait shelf mud (KSSM) off SE Korea, revealed by high-resolution subbottom profiles, is associated with acoustic blanking, acoustic turbidity, seepages with plumes in the water column, and seafloor depressions. The acoustic blanking, characterized by strong, consistent top reflection and wipeout below, is most dominant. The seaward edge of the acoustic blanking zone generally coincides with the 100-m water-depth contour, suggesting that the water depth (the pressure) may control the distribution of shallow gas. The acoustic turbidity, characterized by diffuse top reflection, is a dark smear, partially blanking the data below. The seepages with plumes, characterized by vertical smearing and disturbed seafloor, are seen only along the shallowest, landward edge of the acoustic blanking zone. This may suggest that the decreased gas solubility at shallow water depths, caused by the lowered pressure, increases the volume of free gas in the sediments, facilitating the gas escape. The seafloor depressions, interpreted as pockmarks, are accompanied by cone-shaped acoustic masking, which is probably the reflection from a narrow vent of gas. The gas-related acoustic anomalies appear to occur mostly in the upper, recent mud of the KSSM. Neither permeable beds nor faults, which can act as vertical migration pathways for deep thermogenic gas, are evident in the recent mud. We interpret that the bacterial degradation of organic matter in situ is the main source for the gas in the KSSM. The upwelling off SE Korea may be an important source for the increased organic matter in the area.     

中国东海和韩国马山湾海域2株原甲藻的形态结构和分子序列比较

对采自我国东海温岭海域和韩国南部马山湾海域的2株原甲藻进行了藻种分离、纯化培养及rDNA ITS分子序列的PCR扩增与测序,并运用显微镜、扫描电镜、Jukes-Cantor距离矩阵及构建的系统发育树,比较研究了2株原甲藻的形态结构和分子序列.结果表明:温岭藻株(LAMB090508)和马山湾藻株(PDKS0206)具有...     

Diurnal Variations of Summer Precipitation in the Beijing Area and the Possible Effect of Topography and Urbanization

The present study examined the diurnal variations of summer precipitation in the Beijing area by using subdaily precipitation and wind observations. A combined effect of topography and urbanization on the characteristics of diurnal variations was suggested. It was shown that stations located in the plain areaexhibited typical night rain peaks, whereas those in the mountainous area exhibited clear afternoon peaks ofprecipitation diurnal variations. The precipitation peaks were associated with wind fields around the Beijing area, which were found to be highly modulated by mountain-valley circulation and urban-country circulation.The lower-tropospheric wind exhibited a clear diurnal shift in its direction from north at 0800 LST to southat 2000 LST, which reflected mountain-valley circulation. The transitions from valley to mountain windand the opposite generally happened after sunset and sunrise, respectively, and both occurred earlier for thestations located closer to mountains. By comparing the diurnal variations of precipitation at stations in anortheast suburb, an urban area, and a southwest suburb, it was revealed that the northeast suburb grouphad the highest normalized rainfall frequency, but the southwest group had the lowest from late afternoon tolate evening. On the contrary, in the early morning from about 0200 to 1000 LST, the southwest group andurban group had the highest normalized rainfall frequency. This pattern might originate from the combined effects of mountain-valley topography and urbanization.     

韩国的乡村林木与农业生物多样性(英文)

韩国的乡村林木处于偏远村庄附近,单独的树木或一片树林,往往构成风水因素。乡村林木也有野生动物生境的功能,有益于农业生物多样性。本文中,乡村林木分为4种类型(天然林、半天然林、半人工林、人工林)23个主要树种(优势种或次优势种)。赤松(Pinus densiflora)在50个地点是优势种,光叶榉(Zelkova serrata)在45个地点为优势种。乡村林木立地植物共分125科、519属、1081种。尽管乡村林木占地面积极小,占100 000 km2韩国国土面积的0.00278%,但这种生态系统具有重要的生物多样性和生境保护功能。乡村林木不仅是保育生物多样性的一个基础,还能为韩国提供生态系统服务。     

Storm-influenced siliciclastic and carbonate ramp deposits, the Lower Ordovician Dumugol Formation, South Korea

The Dumugol Formation (Lower Ordovician) in the southern part of the Baegunsan syncline, South Korea, contains mixed siliciclastic and carbonate ramp deposits. The ramp sediments were frequently influenced by storm events resulting in tempestites of sandstone-mudstone couplets, bioclastic grainstones to packstones, flat-pebble conglomerates, a skeletal lag layer and laminated calcisiltites. All tempestites are characterized by an erosive to sharp base, poor grading and a transitional upper boundary. The difference in lithology of tempestites appears to have been controlled by the nature of substrates and by proximality. For example, laminated calcisiltites have developed on the shallow carbonate ramp, flat-pebble conglomerates are closely associated with nodular limestones on shallow and deep ramps, and thin skeletal lag layers from fossiliferous argillaceous sediments formed in a basinal setting. The stratigraphic succession of the Dumugol Formation represents an initial transgression followed by a regression. The vertical facies change records the transition from a shallow siliciclastic ramp to a deep carbonate ramp, to a basin, shallowing to a deep carbonate ramp, and to a shallow carbonate ramp. Storm effects are mostly well preserved in shallow to deep ramp deposits.     

Preliminary Results of the Ground-Based Orographic Snow Enhancement Experiment for the Easterly Cold Fog （Cloud） at Daegwallyeong during the 2006 Winter

The snow enhancement experiments, carried out by injecting AgI and water vapor into orographically enhanced clouds (fog), have been conducted to confirm Li and Pitter’s forced condensation process in a natural situation. Nine ground-based experiments have been conducted at Daegwallyeong in the Taebaek Mountains for the easterly foggy days from January–February 2006. We then obtained the optimized condi- tions for the Daegwallyeong region as follows: the small seeding rate (1.04 g min-1) of AgI for the easte...